The invention relates to the field of railway roadbed maintenance, in particular to an expansive pouring device and a method for governing railway roadbed sedimentation and deformation. The expansive pouring device comprises a pouring pile core (1), a containing bag (2) and a slip casting pipe (11), wherein the slip casting pipe (11) is connected on the upper end of the pouring pile core (1) through a sleeved nut (4), the containing bag (2) sleeves the lower end of the pouring pile core (1) through a contracting sealing ring (3), and an expansive ring (12) is arranged on the contact segment of the slip casting pipe (11) and a roadbed (10). The expansive pouring device uses a frame structure supporting principle and a pile type structure principle, expansive foam, slip casting equipment and monitoring equipment are poured by matching with high pressure, the damaged roadbed can be accurately lifted, the accurate degree can realize plus-minus 1mm, the material using rate is high, the government of a large-scale cavity or an underground dark river is also effective, the damage to the roadbed structure is small, and the construction is rapid and convenient.